In the field of nuclear magnetic resonance (NMR), spin echo-based sequences are used to measure many material properties such as relaxivity and diffusivity. These sequences are used in a variety of contexts such as medical imaging, chemical analysis and particularly the characterization of heterogeneous media. Spin echo sequences are particularly valuable when making “ex-situ” measurements, as they tend to be robust in the presence of strong gradients. These sequences are often used in the field of logging (e.g., wireline logging, logging while drilling (LWD) and measurement while drilling (MWD), NMR tools have been used to explore the subsurface based on magnetic interactions with subsurface material. Some downhole NMR logging tools include a magnet assembly that produces a static magnetic field, and an antenna assembly that generates radio-frequency (RF) control signals and detects magnetic resonance phenomena in the subsurface material.
Like reference symbols in the various drawings indicate like elements.